1. Field of the Invention
The present invention relates to a control system for an internal combustion engine provided with an exhaust gas recirculation device for recirculating exhaust gases to an intake system, and particularly to a control system which determines a failure of the exhaust gas recirculation device.
2. Description of the Related Art
A control system, which determines a failure of the exhaust gas recirculation device based on an output of an air-fuel ratio sensor provided in an exhaust system of the engine, is shown in Japanese Patent Laid-open No. 4-101055. In this system, an integrated value ION of the air-fuel ratio sensor output when executing the exhaust gas recirculation, and an integrated value IOFF of the air-fuel ratio sensor output when not executing the exhaust gas recirculation, are calculated. If the difference (IOFF-ION) between the integrated values is equal to or less than a determination value Δ I, it is determined that the exhaust gas recirculation device fails.
In the above-described conventional system, the integrated value obtained by simply integrating the air-fuel ratio sensor output is used for the determination. Therefore, the determination accuracy can be improved.